Any improvement or unit of work when the cost, according to
the estimate of the engineer, will exceed five thousand dollars
($5,000), shall be done by contract let to the lowest responsible
bidder or bidders in the manner provided in this article. The board
shall first determine whether the contract will be let as a single
unit, or will be divided into severable parts, or both, according to
the best interests of the district. The board shall call for bids and
advertise the call pursuant to Section 6066 of the Government Code
in the district, inviting sealed proposals for the construction or
performance of the improvement or before any contract is made. The
call for bids shall state whether the work is to be performed as a
unit or shall be divided into separate specific parts, or both, as
stated in the call. The board may let the work by single contract or
it may divide the work into severable parts by separate contracts, as
stated in the call, according to the best interests of the district.
The board shall require the successful bidder or bidders to file
with the board good and sufficient bonds to be approved by the board
conditioned upon the faithful performance of the contract and upon
the payment of their claims for labor and material, the bonds to
contain the terms and conditions set forth in Title 3 (commencing
with Section 9000) of Part 6 of Division 4 of the Civil Code and to
be subject to the provisions of that title. The board shall also have
the right to reject any bid. In the event no proposals are received
pursuant to advertisement, or the estimated cost of the work does not
exceed five thousand dollars ($5,000), or the work consists of
channel protection, maintenance work, or emergency work, the board of
supervisors may, without advertising for bids, have the work done by
day labor, under the direction of the board, by contract, or by a
combination of the two. In case of an emergency, if notice for bids
to let contracts will not be given, the board shall comply with
Chapter 2.5 (commencing with Section 22050). The district may acquire
in the open market without advertising for bids, materials,
equipment, and supplies for use in any work or for any other purpose;
provided, however, that materials and supplies for use in any new
construction work or improvement, except work referred to in the
preceding sentence, may not be purchased if the cost exceeds five
thousand dollars ($5,000), without advertising for bids and awarding
the contract to the lowest responsible bidder.